Evidence from earlier studies at the protein level indicate that amylase is stored and secreted by three human salivary glands, the parotid, submandibular and sublingual. Using molecular probes which have been developed in our laboratory, we propose to determine whether amylase messenger RNA is present in each of these human tissues. RNA will be isolated and analyzed by Northern blot in order to compare the size and abundance of the amylase messenger RNAs. Restriction fragments will be isolated from a cosmid clone carrying a human salivary amylase gene and used for nuclease protection experiments in order to map the initiation sites of the transcripts present in each type of salivary gland. The results of these studies will provide information regarding the number of salivary amylase genes which are actively transcribed in these tissues and the mechanisms responsible for their tissue-specific regulation. These studies will contribute to our understanding of the genetic regulation of human salivary secretions.